Trany Problem...Wont move in D

[Trevor]

Originally Posted by pearlm30

Thanks again everyone
I did the filter, bypass stock cooler with B&M cooler and fluid change this morning. I still have the same problem. Dont really know what to do now. I think it could be the one way clutch thats going out. No trany code either.
BTW, when i unplug the resistor, the trany is engaging(selector in D) very very slowly shown by the rpm from the rpm gauge and the car will move forward when brake is released, but give a little gas, the rpm will go up while the car is doing like 10 mile per hour.
plug the resistor back in, selector in D, the trany just rev like in N.
I guess it will need a new trany or I can make it a parts car for my other 3 SVXs.
I really appreciate all the advice you guys provided and what a great forum this is

It is of interest that unplugging the resistor has resulted in a discernible change, which could be aligned with a resulting increase in line pressure.

There is the possibility of a fouled, worn or leaking solenoid valve seat, discernible without removing the transmission. A valve which completes full travel will not show a fault code, even though it is leaking. Solenoid valve "A" would be the first to investigate.

It is interesting that a measure of line pressure is seldom if ever recorded as having been taken, when establishing exact transmission faults.

[Trevor]

Originally Posted by crazyhorse

If it can be manually shifted into every gear, and pull. This doesn't sound like a mechanical fault. It sounds electronic.


As it sits, your trans isn't doing anything that would indicate you need to change it. Your TCU, on the other hand IS acting flaky.

It has now been reported that there are no fault codes registered via the transmission and although the procedure is quite complicated, we must accept that this as correct.

The most significant statement remains as:-

"When speed reached about 30, I then move the shifter to 3 and then D and everything is fine including the TC locking at proper speed."

Speed sensors transmit a signal in the form of a voltage pulse so that these can not affect calibration. This leaves the TCU as logically suspect, as was noted in the above post.

[pearlm30]

Hi Tom/Trevor and everyone
I tried to shift to 1 and I can feel the 1 is engaging as normal, but then shifted to D, the trany seems to hold the engagement for a while(3 to 5 sec).
Also tried the opposit, I moved the shifter to D, very slow engagement or trying to engage then I proceed to 2 or 1, then I can feel the proper trany engagment.
All the above done with trany resistor unpluged. If I plug it back in, the trany wont even trying to engage when shift to D but still engaging in 1 or 2 normally. Line pressureand and solenoid A valve as Trevor mentioned? But why would the trany shift fine when higher speed was gain in D even TC would lock up
As far as TCU goes, I have a spare one from 92, but dont think it would fit the 95 since its a OBD2. Can someone confirm this for me?
Where is this inhibitor switch at?
Thanks again

Originally Posted by TomsSVX

Has anyone thought that maybe the inhibitor switch may be at fault? If you can, test continuity in the switch in the D and 3 ranges when shifting from park->D and then from D->3. If there is full continuity in the switch, you may disregard my suggestions. A simple suggestion would be to move the shifter all the way back to 1 and then up to D or 3 to see if this helps... Its worth a shot

Tom

[pearlm30]

Decided to go for a long test drive to get all the Lucas and Type F fluid mixed up properly(car was parked over night). Back up the driveway and put it in D, everything seems ok. Shift nicely, no slip. Went thru a few stop lights and everything was normal. Went into a gas station to get some gas, put in P(I did not shut off engine). After refilling, put in D and everything still normal. Went for about 20 miles of drive, everything was great(no slip, TC lock up normally).
I decided to go and air up the tires since its been parked for a while. Shifted to Park(didnt shut off engine). Finishing up, shifted to R and then D. It started again, just rev in D. Had to shift 1 and 2 to get back home
Can this be temp related? (BTW the outside air temp was 78F)
Why is the trany lost line pressure when shifted to N or P when trany fluid is hot?(I am assuming its the line pressure)

[TomsSVX]

I am going to be honest, this sounds like you are having low line pressure more than anything else. I just do not understand the connection between the difference of manually selecting 1/2 and 3/D. I really need you to check the inhibitor switch on the side of the trans... My best guess is that it is showing some kind of resistance in D and 3 that it is not seeing in 1 and 2. This is a strange issue you are having but the fact that it works properly at some times and not at others is leading me to believe it lacks a physical issue and may be confined to an electrical problem, fingers crossed. Do you have the schematics for the inhibitor switch and/or an ohmmeter??

Tom

[pearlm30]

Thanks Tom
I do have an ohmmeter and I can get the inhibitor switch from my other good working SVXs. Where is this switch located (which side of the trany?)and what did it look like?I dont have the schematics.

Originally Posted by TomsSVX

I am going to be honest, this sounds like you are having low line pressure more than anything else. I just do not understand the connection between the difference of manually selecting 1/2 and 3/D. I really need you to check the inhibitor switch on the side of the trans... My best guess is that it is showing some kind of resistance in D and 3 that it is not seeing in 1 and 2. This is a strange issue you are having but the fact that it works properly at some times and not at others is leading me to believe it lacks a physical issue and may be confined to an electrical problem, fingers crossed. Do you have the schematics for the inhibitor switch and/or an ohmmeter??

Tom

[TomsSVX]

The switch is located on the RH side of the trans. It is what the shifter cable attaches to. Basically it tells everything inside the car what gear has been selected. If it has a weak connection in D and 3 this may be your problem... Worth a shot as it will be a simple/cheap fix

Tom

[Trevor]

Tom is correct to now suspect an intermittent fault which could involve line pressure.

I repeat my post NO. 18 which involved careful thought:-

It is of interest that unplugging the resistor has resulted in a discernible change, which could be aligned with a resulting increase in line pressure.

There is the possibility of a fouled, worn or leaking solenoid valve seat, discernible without removing the transmission. A valve which completes full travel will not show a fault code, even though it is leaking. Solenoid valve "A" would be the first to investigate.

It is interesting that a measure of line pressure is seldom if ever recorded as having been taken, when establishing exact transmission faults.


Intermittent faults are an absolute curse and you must proceed logically rather than stab hit and miss. A proper check on line pressure will save you a lot of heart ache. This procedure should not cost an arm and a leg, but do not let a shop talk you into an extensive transmission overhaul at this stage.

Checking the inhibitor switch for an intermittent electrical fault will require considerable know how and expertise. First off check for any play or irregular mechanical operation when the select lever is moved through all positions.

Describing exactly how to check all electrical connections, contact sequences, as well as for possible poor contacts, will be very involved. Conatact resistance is best checked using a simple test lamp, rather than an ohm meter. I can set out the procedure, but you must accept that it will be very tedious. Therefore a check on line pressure should best take precedence.

[TomsSVX]

Originally Posted by Trevor

Tom is correct to now suspect an intermittent fault which could involve line pressure.

I repeat my post NO. 18 which involved careful thought:-

It is of interest that unplugging the resistor has resulted in a discernible change, which could be aligned with a resulting increase in line pressure.

There is the possibility of a fouled, worn or leaking solenoid valve seat, discernible without removing the transmission. A valve which completes full travel will not show a fault code, even though it is leaking. Solenoid valve "A" would be the first to investigate.

It is interesting that a measure of line pressure is seldom if ever recorded as having been taken, when establishing exact transmission faults.


Intermittent faults are an absolute curse and you must proceed logically rather than stab hit and miss. A proper check on line pressure will save you a lot of heart ache. This procedure should not cost an arm and a leg, but do not let a shop talk you into an extensive transmission overhaul at this stage.

Checking the inhibitor switch for an intermittent electrical fault will require considerable know how and expertise. First off check for any play or irregular mechanical operation when the select lever is moved through all positions.

Describing exactly how to check all electrical connections, contact sequences, as well as for possible poor contacts, will be very involved. Conatact resistance is best checked using a simple test lamp, rather than an ohm meter. I can set out the procedure, but you must accept that it will be very tedious. Therefore a check on line pressure should best take precedence.

Thats just the problem Trevor, I figured a line pressure test would be more involved than checking the switch. The problem here is as follows, the switch is doing something... allowing the car to partially engage in gear, which means a test light may not help since some contact will be made. So a test of the actual resistance may yield a more confident answer.

Tom

[Trevor]

Originally Posted by TomsSVX

Thats just the problem Trevor, I figured a line pressure test would be more involved than checking the switch. The problem here is as follows, the switch is doing something... allowing the car to partially engage in gear, which means a test light may not help since some contact will be made. So a test of the actual resistance may yield a more confident answer.

Tom

A test light will draw significant current and will show up a faulty contact of low resistance. An ohm meter draws bugger all current and will not break down or show up what can exist as a very low resistance contact fault. Both Beav and I have been pointing this out for years and for very good reason.

Twelve connections and seven switch positions are involved and access to the plug socket is far from convenient. A first off careful intuitive mechanical check could disclose faulty alignment, play or whatever.

[pearlm30]

Looks like its held by 3 8mm bolts and a big bolt from the shifter bracket have to come off in order for the switch to be removed?! Can you confirm this?
BTW you mentioned the inhibitor switch tell inside the car what gear, do you meanit tells ECU and the instrument panel?
I did see changes in RPM when I shifted the shifter selector from P or N to D. does that means the switch is good?
Also if ECU is interchangeable between 92 and 95 in case its the ECU fault?
Thanks again

Originally Posted by TomsSVX

The switch is located on the RH side of the trans. It is what the shifter cable attaches to. Basically it tells everything inside the car what gear has been selected. If it has a weak connection in D and 3 this may be your problem... Worth a shot as it will be a simple/cheap fix

Tom

[oab_au]

Originally Posted by pearlm30

Looks like its held by 3 8mm bolts and a big bolt from the shifter bracket have to come off in order for the switch to be removed?! Can you confirm this?
BTW you mentioned the inhibitor switch tell inside the car what gear, do you meanit tells ECU and the instrument panel?
I did see changes in RPM when I shifted the shifter selector from P or N to D. does that means the switch is good?
Also if ECU is interchangeable between 92 and 95 in case its the ECU fault?
Thanks again

I think you can discount the Shifter alignment as the shifter will select 1st/Rev, N, and P, using the Manual valve in the gear box.
The Inhibitor switch also. If it brings on the gear position lights on the dash, when you move it through the gear positions, it will be sending the same signal to the TCU as they are both triggered by the same signal.

The line pressure is fine when you select 1st/Reverse, and when you run the speed up to pick up 3rd and 4th, in the D position.

The TCU plays no real part in the selection of 1st gear in either 1st in D, or 1st selected. They are both engaged by the Manual valve, moved by the shift lever.
In D the valve turns on the Forward clutch. In 1st selected, the manual valve turns on the Forward clutch and the low/Reverse brake.

As I said before, the only functional difference between 1st position when in D, and 1st position selected with the lever is, when 1st is selected, the Low/Reverse brake takes the place of the slipping 1/2 one way clutch.

Harvey.

[pearlm30]

So Harvey, you are saying my one way cluth is bad/slipping? Can you provide a reason as why when the car is cold(park over night) then it drives as normal for over 20 miles(getting trany fluid to normal operating temp) but once I park and shift the selector to P or N, then it would acting up again

Originally Posted by oab_au

I think you can discount the Shifter alignment as the shifter will select 1st/Rev, N, and P, using the Manual valve in the gear box.
The Inhibitor switch also. If it brings on the gear position lights on the dash, when you move it through the gear positions, it will be sending the same signal to the TCU as they are both triggered by the same signal.

The line pressure is fine when you select 1st/Reverse, and when you run the speed up to pick up 3rd and 4th, in the D position.

The TCU plays no real part in the selection of 1st gear in either 1st in D, or 1st selected. They are both engaged by the Manual valve, moved by the shift lever.
In D the valve turns on the Forward clutch. In 1st selected, the manual valve turns on the Forward clutch and the low/Reverse clutch.

As I said before, the only functional difference between 1st position when in D, and 1st position selected with the lever is, when 1st is selected, the Low/Reverse clutch takes the place of the slipping 1/2 one way clutch.

Harvey.

[oab_au]

Originally Posted by pearlm30

So Harvey, you are saying my one way cluth is bad/slipping? Can you provide a reason as why when the car is cold(park over night) then it drives as normal for over 20 miles(getting trany fluid to normal operating temp) but once I park and shift the selector to P or N, then it would acting up again

Yes mate, I am saying that the one way clutch is slipping.

No mate, I can't provide a reason for the way its acting.

Probably the same reason it was working fine the day before it failed.
It did not break the one way clutch, it is just slipping. It may grip next time also, but as it has slipped, it will do it again.

Harvey.

[Trevor]

Originally Posted by oab_au

The TCU plays no real part in the selection of 1st gear in either 1st in D, or 1st selected. They are both engaged by the Manual valve, moved by the shift lever.
In D the valve turns on the Forward clutch. In 1st selected, the manual valve turns on the Forward clutch and the low/Reverse brake.

As I said before, the only functional difference between 1st position when in D, and 1st position selected with the lever is, when 1st is selected, the Low/Reverse brake takes the place of the slipping 1/2 one way clutch.

Harvey.

It is stated that the manual valve is moved by the shift lever to select first, even when the lever is in D and that the TCU plays no part in the process. What mechanical process is available to engage first with the lever in D

In point of fact the TCU has control when first is not selected by the lever and it is clear that throttle position becomes part of that control. Only when the select lever selects first, is control outside of the influence of the TCU.